void main() {
  print("hello world");

  int age = 18;
  double length = 22.5;
  String name = "aaa";
  bool haveGirlFriend = true;

  // 运行 快捷键 alt + shift + x，或者反手键run
  print("age = $age, length = $length, name = $name, haveGirlFriend = $haveGirlFriend");
}
